It is well known that the heat from electromagnetic radiation with a wavelength in the range of about 0.7 microns to about 5 microns, the near infrared spectrum, can have debilitating effects on many substrates. Damage and deterioration, such as cracking, can develop when a substrate is unprotected. This type of radiation can also cause damage to the eye. There are many sources of electromagnetic radiation in this range of the spectrum The sun is a major source of near infrared electromagnetic radiation, however, other sources include tungsten filaments, fluorescent lamps, welding arcs, and laser light.
Compounds that absorb near infrared (NIR) electromagnetic radiation are also well known in the art. Aminium and diimmunonium salts are examples of such compounds and are described in U.S. Pat. Nos. 3,440,257 and 5,686,639, the contents of which are incorporated herein by reference. These types of infrared absorbing compounds can be regarded as similar in that they strongly absorb energy in the NIR portion of the spectrum, yet they transmit light in the visible portion of the spectrum (0.4 microns to 0.7 microns). Because of these properties, U.S. Pat. No. 3,440,257 teaches incorporating its NIR absorbing compounds into plastics for use in sunglasses, welding goggles, laser protection eyewear, and other products that shield the eye from the harmfull effects of NIR radiation. These types of compounds can also be incorporated into other plastics to protect inanimate objects from hazardous NIR radiation, such as in projection lenses or television filters.
Wax and polish compositions have also been developed which contain compounds that absorb NIR radiation or other electromagnetic radiation, such as microwaves and radio waves. These waxes and polishes can be used to provide a protective layer to painted surfaces, such as automobile body parts, to attenuate the cracking and fading effects NIR radiation can have on such surfaces. Waxes and polishes containing NIR radiation absorbing compounds have also been used for other purposes such as to defeat near infrared laser detection mechanisms by absorbing and diminishing the reflection of NIR radiation.
However, waxes and polishes have drawbacks. Waxes and polishes often wash away easily after only short-term exposure to wet weather conditions. Most wax and polish compositions will provide an extremely thin coating which will often necessitate reapplication in order to provide greater absorbency. However, such reapplication of wax or polish coatings is usually not successful in achieving the necessary absorbency. Furthermore, polishes can be messy and waxes require rubbing and buffing, making application time consuming in most instances.
Thus, there exists a need in the art for a relatively inexpensive, easy to apply, weather-resistant, electromagnetic radiation absorbing coating composition which exhibits good absorbency of NIR radiation and yet still transmits a substantial portion of visible light.
The present invention relates to compositions, useful as coatings, which contain a near infrared (NIR) electromagnetic radiation absorbing agent. More particularly, the present invention relates to liquid compositions, containing an NIR absorbing agent, which can be applied to a surface as a roughly uniform coating having a particular thickness for the purpose of absorbing NIR electromagnetic radiation.
The present invention provides a relatively inexpensive coating composition which exhibits a high degree of NIR absorption, a high degree of visible light transmittance, and is both easy to apply and weather-resistant.
The invention includes a liquid composition for coating surfaces which comprises a near infrared absorbing agent present in an amount of about 0.01% to about 2% by weight, a carrier vehicle present in an amount of about 20% to about 60% by weight, and a solvent system present in an amount of about 40% to about 80% by weight, each based upon the total weight of the composition.
The invention also includes a liquid composition for coating surfaces comprising (a) a near infrared absorbing agent selected from the group consisting of compounds of the formula (I):
[(R2NZ)2Nxe2x95x90Zxe2x80x2xe2x95x90NR2]2+2Xxe2x88x92xe2x80x83xe2x80x83(I)
wherein R is an alkyl group of about 1 to about 6 carbon atoms; Z is a divalent phenyl which may or may not be ring substituted with one or more alkyl alkoxy, halogen, nitro, cyano, and carboalkoxy groups; Zxe2x80x2 is a quinoidal phenyl which may or may not be ring substituted with one or more alkyl, alkoxy, halogen, nitro, cyano, and carboalkoxy groups; and X is an anion of a strong acid, and compounds of the formula (II):
[(R2NZ)3N]++Xxe2x88x92xe2x80x83xe2x80x83(II)
wherein R is an alkyl group of about 1 to about 6 carbon atoms; Z is a divalent phenyl which may or may not be ring substituted with one or more alkyl, alkoxy, halogen, nitro, cyano, and carboalkoxy groups; and X is an anion of a strong acid; (b) a carrier vehicle comprising a copolymer formed by polymerization of:
(i) about 45% to about 55% by weight butyl acrylate,
(ii) about 38% to about 45% by weight methylmethacrylate,
(iii) about 4% to about 10% by weight hydroxyethylmethacrylate,
(iv) about 0% to about 8% by weight methacrylic acid, and
(v) about 0% to about 2% by weight acrylic acid; and (c) a solvent system.
In one embodiment of such a liquid composition for coating surfaces, the carrier vehicle (b) may comprise a copolymer formed by polymerization of
(i) about 40% to about 70% by weight methylmethacrylate by weight,
(ii) about 10% to about 30% by weight ethylacrylate, and
(iii) about 20% to about 30% by weight dimethylaminoethylmetacrylate, each based upon the total weight of the copolymer.
Further, the invention includes a method of reducing the reflection of near infrared radiation from a surface, comprising applying to the surface, a liquid composition which comprises a near infrared absorbing agent, a carrier vehicle, and a solvent system; and removing the solvent system, whereby a near-infrared absorbent coating is provided on the surface.
The invention also includes a surface having a coating with a thickness of about 0.25 mil to about 2 mil, comprising a near infrared absorbing agent, and a carrier vehicle, wherein the thickness is measured in a direction transverse to the surface.
The invention also includes a copolymer useful as a carrier vehicle, said copolymer prepared by polymerizing:
(a) about 45% to about 55% by weight butyl acrylate,
(b) about 38% to about 45% by weight methylmethacrylate,
(c) about 4% to about 10% by weight hydroxyethylmethacrylate,
(d) about 0% to about 8% by weight methacrylic acid, and
(e) about 0% to about 2% by weight acrylic acid.
The invention also provides a copolymer useful as a carrier vehicle, said copolymer prepared by polymerizing:
(a) about 40% to about 70% by weight methylmethacrylate,
(b) about 10% to about 30% by weight ethylacrylate,
(c) about 20% to about 30% by weight.
Furthermore, the invention includes a method of producing a copolymer useful as a carrier vehicle, said method comprising polymerizing:
(a) about 45% to about 55% by weight butyl acrylate,
(b) about 38% to about 45% by weight methylmethacrylate,
(c) about 4% to about 10% by weight hydroxyethylmethacrylate,
(d) about 0% to about 8% by weight methacrylic acid, and
(e) about 0% to about 2% by weight acrylic acid.
A method of producing a copolymer useful as a carrier vehicle, said method comprising polymerizing:
(a) about 40% to about 70% by weight methylmethacrylate,
(b) about 10% to about 30% by weight ethylacrylate,
(c) about 20% to about 30% by weight dimethylaminoethylmetacrylate, is also provided by the present invention.